davie and horatio are riding their motorbikes on a scenic tour that is 80 miles long. davie rides at 20…

Explanation:

Step1: Calculate Davie's time

Use formula $t = \frac{d}{v}$, where $d = 80$ miles and $v = 20$ mph. So $t_{Davie}=\frac{80}{20}=4$ hours.

Step2: Adjust for Davie's head - start

Davie leaves 90 minutes (or 1.5 hours) before Horatio. So Horatio's time $t_{Horatio}=4 - 1.5=2.5$ hours.

Step3: Calculate Horatio's speed

Use formula $v=\frac{d}{t}$, with $d = 80$ miles and $t = 2.5$ hours. So $v_{Horatio}=\frac{80}{2.5}=32$ mph.

Answer:

C. 32 mph